Peptide Backbone Conformation Affects the Substrate Preference of Protein Arginine Methyltransferase I

• Published in: Biochemistry (Easton) Vol. 51; no. 27; pp. 5463 - 5475
• Main Authors: Kölbel, Knut, Ihling, Christian, Kühn, Uwe, Neundorf, Ines, Otto, Silke, Stichel, Jan, Robaa, Dina, Beck-Sickinger, Annette G, Sinz, Andrea, Wahle, Elmar
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 10-07-2012
• Subjects: Amino Acid Motifs; Amino Acid Sequence; Animals; Biocatalysis; Humans; Methylation; Models, Molecular; Molecular Sequence Data; Mutagenesis, Site-Directed; Mutation; Peptide Fragments - chemistry; Peptide Fragments - metabolism; Peptides - chemistry; Poly(A)-Binding Protein II - chemistry; Poly(A)-Binding Protein II - genetics; Proline; Protein-Arginine N-Methyltransferases - chemistry; Protein-Arginine N-Methyltransferases - metabolism; Rats; Repressor Proteins - chemistry; Repressor Proteins - metabolism; Substrate Specificity
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi300373b

Asymmetric dimethylation of arginine side chains is a common post-translational modification of eukaryotic proteins, which serves mostly to regulate protein–protein interactions. The modification is catalyzed by type I protein arginine methyltransferases, PRMT1 being the predominant member of the family. Determinants of substrate specificity of these enzymes are poorly understood. The Nuclear poly(A) binding protein 1 (PABPN1) is methylated by PRMT1 at 13 arginine residues located in RXR sequences in the protein’s C-terminal domain. We have identified a preferred site for PRMT1-catalyzed methylation in PABPN1 and in a corresponding synthetic peptide. Variants of these substrates were analyzed by steady-state kinetic analysis and mass spectrometry. The data indicate that initial methylation is directed toward the preferred arginine residue by an N-terminally adjacent proline. Enhanced methylation upon peptide cyclization suggests that induction of a reverse turn structure is the basis for the ability of the respective proline residue to enable preferred methylation of the neighboring arginine residue, and this notion is supported by far-UV circular dichroism spectroscopy. We suggest that the formation of a reverse turn facilitates the access of arginine side chains to the active sites of PRMT1, which are located in the central cavity of a doughnut-shaped PRMT1 homodimer.